Currently, in many electronic industry fields, such as the manufacture of LCD touch panels, adhesives are used to bond various substrates and assemblies. Conventional adhesives used in such an application are ultraviolet (UV)-curable adhesives. However, complicated and special designs and opaque parts, such as those caused by ceramics and metals result in transparent areas and nontransparent shadow areas in display panel and touch panel devices. Since UV irradiation cannot efficiently reach the nontransparent shadow areas in the device when UV irradiation is used, the need for practical manufacture application cannot be fulfilled by means of typical UV-cure adhesives.
To solve the problem, there has been research attempting to use adhesives possessing both UV-cure and thermal-cure properties. For example, US20020198279 A1 discloses a UV-cure and thermal-cure adhesive. The adhesive composition comprises at least one of acrylate monomer, an acrylate oligomer and a thermal initiator. The adhesive composition is used as an adhesive for flat panel displays and optoelectronics components.
Besides the UV-cure adhesive and thermal-cure adhesive, moisture-cure adhesives are also conventional adhesives which can bond various kinds of substrates. For example, U.S. Pat. No. 7,060,750 B2 discloses an adhesive, sealant or coating composition, which comprises polyether urethanes containing reactive silane groups, i.e. silane-terminated polyurethanes. The composition can be moisture-cured in the presence of moisture-curing catalysts, such as titanates and organotin compounds, etc.
U.S. Pat. No. 6,828,355 B1 discloses a composition which can be both UV cured and moisture-cured. Such composition includes a polyorganosiloxane, having photocurable groups, such as (meth)acrylate and/or moisture-curable groups, such as alkoxy or aryloxy groups. The composition further includes a photoinitiator and moisture-cure catalyst such as organic titanium, organic tin and zirconium complexes. The composition can be used in the art of sealing and encapsulating of integrated circuits.
Due to the requirements related to bonding complicated-structure devices with both transparent and nontransparent areas in the field of panel display, touch panel and optoelectronics components, there is a continuing need for providing an easily applicable adhesive with combined cure functions. In addition to possess the above-mentioned quality, i.e., cure in the nontransparent areas, the adhesive must also have good qualities after being cured, such as: larger than about 90% of transparency, less than about 1% of haze, less than about 1 of b value, about 0.2-about 1.5 MPa adhesion strength and a viscosity adjustable over a large range.